The present invention relates to an optical switch that decides the optical paths of input light coming from input ports and outputs the light from output ports, in particular to an optical switch of autonomous hardware capable of outputting input light coming from arbitrary input ports from arbitrary output ports and a method for controlling the optical paths thereof.
A method of transmitting optical signals by passing the light itself through optical paths without applying photoelectric conversion in optical path controlling is disclosed in JP-A No. 320527/2004 (refer to FIGS. 6 and 7 for example).
In the method, an optical wavelength router is provided with: M units of demultiplexing circuits which are allocated in accordance with input ports and demultiplex M-way wavelength multiplexing light signals into the light signals of individual wavelengths; M units of multiplexing circuits which are allocated in accordance with output ports and multiplex M kinds of light signals having different wavelengths; and M-square (M×M) units of optical paths which connect the demultiplexing circuits to the multiplexing circuits so that M units of transceivers optically interconnected to the input and output ports are in the state of full-mesh connection.
By such a configuration, even in the case of increasing or decreasing the number of transceivers connected to an optical wavelength router, it is basically possible to construct a full-mesh network having wavelength cyclicity only by changing a connection mode of the optical paths of the optical wavelength router. Therefore, it is not necessary to change the optical wavelength router itself to another optical wavelength router when the number of the transceivers is increased or decreased. As a consequence, the aforementioned configuration has very high flexibility in response to the decrease or increase of the number of transceivers.
Here, in the configuration, with regard to the optical paths connecting M units of demultiplexing circuits to M units of multiplexing circuits, one line of an optical path is fixedly allocated to each wavelength.
Further, since the configuration has wavelength cyclicity, a port and a wavelength are uniquely related under the circumstance of wavelength multiplexing signals and it is possible to enhance the wavelength utilization efficiency without causing the collision of wavelengths in an identical port.
In the method disclosed in JP-A No. 320527/2004, the wavelength of an optical signal and the port thereof are in the relation of one to one and the relation between them is invariable, and hence it is impossible to share an empty source (optical path) among plural paths. As a consequence, the method lacks flexibility.
Hence, it is possible to install only one unit of such a device as disclosed in JP-A No. 320527/2004 in the center and apply the device to a star-shaped network that covers a metro area. However, when such devices are applied to a wide-area mesh network wherein the devices are connected in a multistage form, since the optical signals of different wavelengths in an identical path are inevitably output to different paths, the allocation and control of the paths and wavelengths are hardly secured.
In addition, a device disclosed in JP-A No. 320527/2004 includes passive elements and thus the electric power consumption is kept low. However, it may be difficult to know the usage of the paths including output ports and thus the device cannot deal with the case where the usage of paths must be grasped.